Catalytic converter

ABSTRACT

A catalytic converter having an improved suspension system for carrying a fragile catalyst housing. The housing is retained within a surrounding casing by a resilient support media which restricts transverse movement of the housing relative to the casing. Destructive longitudinal housing movement is also prevented by the support media in conjunction with the respective shapes of the housing and casing. In a preferred embodiment the casing is strengthened by tapering from a larger cross-section at the middle to a smaller one at the ends, while the housing is of uniform cross-section throughout. Various other combinations of housing and casing shapes are possible which similarly retard housing movement.

United States Patent [191 Kearsley Oct. 14, 1975 CATALYTIC CONVERTER3,817,714 6 1974 Wiley 23/288 FC [75] Inventor: 2 32211123811. Kearsley,Chatham, Primary Examiner Barry S- Richman Assistant ExaminerMichael S.Marcus [73] Assignee: Fram Corporation, East Providence,

R1. [57] ABSTRACT 2 Filed: 13, 1972 A catalytic converter having animproved suspension Appl. No.: 314,511

system for carrying a fragile catalyst housing. The housing is retainedwithin a surrounding casing by a resilient support media which restrictstransverse movement of the housing relative to the casing. De-

. structive longitudinal housing movement is also prevented by thesupport media in conjunction with the respective shapes of the housingand casing. in a preferred embodiment the casing is strengthened bytapering froma' larger cross-section at the middle to a smaller one atthe ends, while the housing is of uniform cross-section throughout.Various other combinations of housing and easing shapes are possiblewhich similarly retard housing movement.

2 Claims, 6 Drawing Figures US. Patent 0012. 14, 1975 Sheet 1 0123,912,459

FIG.

FIG. 2

U.S. Patent Oct. 14, 1975 Sheet 2 of 2 3,912,459

FIG. 6

CATALYTIC CONVERTER BACKGROUND OF THE INVENTION 1. Field of thelnvention This invention relates to the catalytic purification ofexhaust gases from an internal combustion engine, and more particularlyto apparatus for supporting within a casing a fragile housing forcatalyst material against destructive vibrationsboth longitudinal andtransverse.

2. Description of the Prior Art The attainment of more completecombustion of products fed to an internal combustion engine in order topurify the exhaust gases delivered therefrom has been an object of greatinterest, particularly with regard to automotive vehicles. The problemof air pollution caused by incomplete combustion is well known. To thisend catalytic converters have been developed to consume incompletelyoxidized gases exhausted from the engine. Typically employing a fragileceramic housing for the catalyst material, the converter is held in ametallic casing and installed in the line of exhaust gas flow downstreamfrom the engine. Gases flow through the catalyst material and areoxidized. To prevent untreated gases from escaping into the gap betweenthe housing and casing, sealing rings or the like are used at either endof the housing. The rings are also designed to bear against the ends ofthe housing to prevent longitudinal motion.

A flexible mesh support has been used around the periphery of thecatalyst housing to protect it from vibrating against the hardcasingsurface during operation. This is especially important at the hightemperatures necessary to completely burn the exhaust gases, at whichthe casing expands transversely away from the catalyst housing. Aneffective solution to transverse vibration is thus provided, but theusefulness of the system has been considerably limited becauselongitudinal vibration can still develop.

While the mesh support also provides some resistence to longitudinalhousing motion, it will not prevent the housing from vibrating acrossany small gap that might exist between it and the sealing rings. If sucha gap should be formed, a destructive sequence may be initiated when theautomobile is operated; the ceramic housing vibrates against the sealingrings and begins to crumble at the points of contact. The gap widensaccordingly, leading to greatervibrations and more housing crumbling,until the mesh support itself wears the housing. Rapid failure of theconverter follows.

The aforementioned high operating temperatures contribute se riously tothe formation of such gaps since the outer casing undergoes a greaterthermal expansion than does the catalyst housing, moving the sealingrings away from the housing even if a close fit had been achievedinitially. In addition, this movement also admits exhaust gases into thespace between the casing and housing, bypassing the catalyst material.Lack of adequate means to prevent longitudinal movement is particularlytroublesome, as the ceramic housings are stronger in transversecompression than in longitudinal compression applied at the ends.

SUMMARY OF THE INVENTION It is a principal object of the presentinvention to provide a new and improved catalytic converter that willavoid harmful longitudinal vibrations of the catalyst housing, evenunder sustained operation at high temperatures. It is a furtherobjecttoprovide a new and improved catalytic converter with a shaped housing forcatalyst material and ashaped outer casing, designed to hold a resilientsupport media therebetween in such a way as to arrest both longitudinaland transverse motion of the housing relative to the casing.

In the accomplishment of these objects the housing and casing in acatalytic converter of the type described are shaped such that anannular opening is formed therebetween, at least one of said housing andsaid casing having non-uniform transverse dimensions in longitudinalcross-section. Any longitudinal movement of the housing away from anequilibrium position causes a compression of a portion of thesurrounding support media. The compression is translated into adistributed generally transverse force acting upon the housing surfacethat dampens longitudinal vibrations and restores the housing toequilibrium. In a preferred embodiment the casing is tapered from alarger cross-section in the middle to smaller cross-sections at eachend, while the catalyst housing is of uniform cross-sectional dimensionsthroughout. The support media is compressed into mirror-image generallywedge shapes, of which one wedge is narrowed and compressed by anylongitudinal housing displacement and tends to restore the housing toits original position. lf the casing is rectangular, its side walls maybe left untapered, the taper at the top and bottom generally beingadequate to prevent undesired motion. The tapered walls are easy tomanufacture and provide greater strength than the prior art straightwalls.

Other gradual constrictions in the gap between casing and housing maylikewise create an area of greater compression in the support media thatwill resist longitudinal movement of the housing. Either the casingalone or both casing and housing may be tapered either outwardly orinwardly, or other areas of compression may be provided. In general,V-shaped shells are preferred for strength, ease of manufacture, andeffectiveness. If the support media is compressed sufficiently at itsends, exhaust gases will be unable to enter the gap and the need forsealing rings or gas flow deflectors eliminated.

Another object can thus be seen to be the provision of a catalyticconverter that can operate under heavy vibrational loading withoutdestruction of the catalyst housing.

Still another object is the provision of a catalytic converter with astrengthened casing that eliminates the need'for sealing rings at thecatalyst housing. A related object is the provision of a catalyticconverter that can be used with sealing rings without destructivelongitudinal vibrations against the rings.

Other objects, features and advantages of this invention will occur tothose skilled in the art from the following detailed description ofpreferred embodiments thereof taken together with the accompanyingdrawings in which,

FIG. 1 is a side elevation, partly in section, showing a tapered casingand straight housing for a catalytic converter in accordance with theinvention;

FIGS. 2 and 3 are sectional views taken respectively along the lines 22and 3-3 of FIG. 1;

FIG. 4 is a side elevation, partly in section, showing a cylindricalembodiment of the invention with a strengthened casing and sealingrings;

FIGS. and 6 are views similar to FIG. 1 showing variations in the casingand housing shapes.

Detailed Description In FIGS. 1 2 and 3 is shown a preferred embodimentof a catalytic converter 10, according to the invention, having anexhaust gas inlet port 12 to receive the exhaust from an internalcombustion engine, an outlet 14 leading towards a tail-pipe, and acentral metallic casing portion 16. The casing 16 is generallyrectangular in cross-section with I/l6 walls, formed from upper andlower sections welded together at flanges 18 running longitudinallyalong its sides. A boss 20 may be placed along the upper side forsecuring the converter to the vehicle or machine. An open-ended ceramichousing 22 is located inside and spaced from the inner walls of casing16 by a resilient support media 26. Catalyst material is mounted on theexposed surfaces of a longitudinally channeled ceramic honeycomb 24,each channel having a gas inlet and outlet. Exhaust gas enters theconverter through inlet port 12 and is purified during transit throughthe channels by contact with the catalyst material contained therein.

The support media 26 is a shock absorbant material, capable ofwithstanding elevated temperature conditions, and is held undercompression in non-sliding contact with the exterior housing 22 walls.It may be a corrugated, knitted mesh metallic fabric such as stainlesssteel that is knitted into a sock and then flattened and crimped at theends. To prevent slippage relative to the housing 22 the strands of wiremesh dig into the ceramic housing surface, which may also be roughenedor corrugated for even greater contact. Spring plates may also be usedfor the support media 26, with small barbs extending into the ceramic.While it is not necessary that the support media 26 extend all the wayaround the housing 22, full wrap around facilitates manufacture.

In the preferred embodiment shown, designed for use on automobiles, thehousing 22 extends beyond the support media 26 by approximately A ateach end. The casing 16 tapers away from the center at top and bottom atan inward angle of approximately 5,while the housing 22 has straightupper and lower surfaces. A gap approximately 0.2" wide, into which thesupport media 26 fits, separates the casing 16 from the housing 22 atthe middle 28 thereof; the gap is narrowed to approximately 0.l at eachcasing end 30. The support media 26 is thereby subjected to a lessercompression at the middle and to increasing compression as theextremeties are approached. It in turn exerts a corresponding pressureupon the housing 22.

The support media 26 is squeezed into mirror image wedge-like shapes,wide at the middle 28 and narrow at each end, and shields the fragilehousing 22 from contact with the metallic casing 16 under transversevibrations. The housing 22, however, is particularly susceptible todamage if it is allowed to vibrate freely in a longitudinal direction,the ends 30 breaking easily when struck against a hard object. Thisproblem was most acute in previous devices when sealing rings were usedto fix a housing in longitudinal position and block exhaust gases fromentering the gap between housing and casing. Thermal expansion duringoperation opened a space across which the housing ends could vibrateonto the sealing rings, ultimately leading to mechanical failure.

The operation of the present invention in arresting destructive grosslongitudinal movement of the ceramic housing 22, best illustrated withreference to FIG. 1, is as follows:

5 Assume the ceramic housing 22 has vibrated slightly to the rightduring operation, so that its right end is at the position indicated bythe dotted line 30a. The support media 26 is also moved partially to theright to 26a, and forced further into the wedge described by theadjacent walls of housing 22 and casing 16. The end of support media 26is now encased in a smaller gap and is hence subjected to a greaterdegree of compression. A corresponding increase in pressure is felt atevery point in the support media that is moved further into the wedge.Frictional and shear forces are set up between the support media 26 andthe inner wall of casing 16, and reflected into increased shear forcesdistributed over the entire right hand surface of the housing 22,tending to pull it back into balanced symmetry within the casing 16. Ineffect, what prior devices would have experienced as a sharp. blowagainst the housing end 30 in a longitudinal direction in translatedinto a distributed transverse pressure that can be handled by thehousing 22 without damage. Even a slight movement is met by acorresponding retaining force exerted by the support media 26. Thepressure continually grows as the movement increases, permitting a rapidresponse to more severe vibrations and limiting longitudinal movement ofthe housing 22 to small amounts even under heavy vibrational loading.

In the above described embodiment a taper was provided only on the upperand lower walls of the casing 16. As this will normally be sufficient toprevent damaging vibrations, the casing side walls may be manufacturedstraight across without any taper as shown in FIGS; 2 and 3. The gapbetween the casing 16 and housing 22 along the sides is preferably asize between that of the smallest and largest gaps provided at the topand bottom. An added benefit of the tapered casing configuration of thisinvention is a strengthening of the catalytic converter under appliedvibrations or load. Extra strength is provided for a casing of givenwall thickness against a commonly encountered phenomona known as oilcanning, a situation in which a flat steel sheet buckles under vibrationor load.

Other embodiments of a catalytic converter in which a support media iscompressed by varying amounts along the surface of the catalyst housingand holds it against longitudinal vibration may now occur to thoseskilled in the art. FIGS. 4-6 illustrate a few of them. In FIG. 4 atapered cylindrical configuration is shown in which a left hand cylinder34 is welded to a right hand cylinder 36 along flanges 38 at the end ofeach cylinder. The two cylinders may also be joined by an overlappingarrangement to provide a casing. A cylindrical housing 40 for catalyticmaterial is located inside the casing and protected by support media 26.The casing is tapered as before, with the exception that the taperingextends all the way around. A plurality of hollow strengthening ribs 44are provided on the surface on the casing 16 to enhance structuraldurability and provide recesses 46 which carry portions of the supportmedia 26 and furtherengage it to the casing. If sealing rings 48 aredesired they may conveniently be provided adjacent the annular openingat each end of the housing 40, with arms 50 extending orthogonally fromthe rings and cemented between the housing 40 and the support media 26.

FIG. 5 shows another variation in which both a casing 52 and a housing54 are provided with similarly tapered walls forming a V-shaped annulargap of substantially constant thickness for support media 26. Thecompression on the housing 54 is essentially constant along its length.and increases uniformly when the housing is moved to the left or right.While this arrangement provides the most widely distributed transverseforce, the housing 54 shown is somewhat more difficult to manufacturethan one of uniform thickness throughout.

In FIG. 6 another embodiment is shown in which a straight housing 56 issurrounded by a casing 58 that is also straight at its mid-section andtapered only at the ends. Because it extends over a lesser distance, theangle of taper is somewhat greater and assists against slippage betweenthe casing 58 and support media 60.

A further advantage is found in those embodiments in which the supportmedia is compressed by a constriction in the gap near the ends of acatalyst housing. The support media may be compressed to a degreesufficient to prevent the entrance of exhaust gases between the casingand housing, thus permitting the converter to be operated with nosealing rings at all; exhaust gases will all flow through the catalysthousing to be treated. lfsealing rings are desired, they may be providedas shown in FIG. 4.

Other embodiments of this invention will occur to those skilled in theart, from the foregoing nonlimiting description of preferred embodimentsthereof.

What is claimed is:

1. In a catalytic converter for exhaust gases of the type having acasing with an internal wall surface and gas inlet and outlet openingsat its respective ends, a fragile housing interior to said casing in theline of exhaust gas flow having exhaust gas passages extendinglongitudinally between and in communication with said inlet and outletopenings and containing catalyst material, said housing having anexterior longitudinal wall surface and being longitudinally movable withrespect to said casing, a resilient support media between and engagingthe exterior longitudinal wall surface of said housing and the interiorwall surface of said casing to support said housing within said casingand limit relative movement therebetween, the improvement comprising theexterior wall surface of said housing and the opposing interior wallsurface of said casing sloping relative to each other in one directionalong one longitudinal portion of said converter, and in the oppositedirection along another portion of said converter to form therebetweenan annular opening having oppositely tapered portions, said supportmedia being lodged in compression in said annular opening, between andin contact with said sloping interior and exterior wall surfaces, saidrelatively sloping walls and said tapered opening therebetween extendingalong a substantial longitudinal portion of said housing, whereby aportion of said support media is subjected to increased compression whensaid housing is moved in a longitudinal direction relative to saidcasing, thereby tending to arrest longitudinal movement of said housingrelative to said casing.

2. In a catalytic converter for exhaust gases of the type having acasing with an internal wall surface and gas inlet and outlet openingsat its respective ends, a fragile housing interior to said casing in theline of exhaust gas flow having exhaust gas passages extendinglongitudinally between and in communication with said inlet and outletopenings and containing catalyst material, said housing having anexterior longitudinal wall surface and being longitudinally movable withrespect to said casing, a resilient support media between and engagingthe exterior longitudinal wall surface of said housing and the interiorwall surface of said casing to support said housing within said casingand limit relative movement therebetween, the improvement conprising theexterior wall surface of said housing and the opposing interior wallsurface of said casing sloping parallel to each other in one directionalong one longitudinal portion of said converter and in the oppositedirection along another longitudinal portion of said converter to formtherebetween an annular opening with oppositely sloping longitudinalportions, said support media being lodged in compression in said annularopening, between and in contact with said sloping interior and exteriorwall surfaces, whereby a portion of said support media is subjected toincreased compression when said housing is moved in a longitudinaldirection relative to said casing, thereby tending to arrestlongitudinal movement of said housing relative to said casing.

1. IN A CATALYTIC CONVERTOR FOR EXHAUST GASES OF THE TYPE HAVING ACASING WITH AN INTERNAL WALL SURFACE AND GAS INLET AND OUTLET OPENINGSAT ITS RESPECTIVE ENDS, A FRAGILE HOUSING INTERIOR TO SAID CASING IN THELINE OF EXHAUST GAS FLOW HAVING EXHAUST GAS PASSAGES EXTENDINGLONGITUDINALLY BETWEEN AND IN COMMUNICATION WITH SAID INLET AND OUTLETOPENINGS AND CONTAINING CATALYST, MATERIAL, SAID HOUSING AN EXTERIORLONGITUDINAL WALL SURFACE AND BEING LONGITUDINALLY MOVABLE WITH RESPECTTO SAID CASING, A RESILIENT SUPPORT MEDIA BETWEEN AND ENGAGING THEEXTERIOR LONGITUDINAL WALL SURFACE OF SAID HOUSING AND THE INTERIOR WALLSURFACE OF SAID CASING TO SUPPORT SAID HOUSING WITHIN SAID CASING ANDLIMIT RELATIVE MOVEMENT THEREBETWEEN THE IMPROVEMENT COMPRISING THEEXTERIOR WALL SURFACE OF SAID HOUSING AND THE OPPOSING INTERIOR WALLSURFACE OF SAID CASING SLOPING RELATIVE TO EACH OTHER IN ONE DIRECTIONALONG ONE LONGITUDINAL PORTION OF SAID CONVERTER, AND IN THE OPPOSITEDIRECTION ALONG ANOTHER PORTION OF SAID CONVERTER TO FORM THEREBETWEENAN ANNULAR OPENING HAVING OPPOSITELY TAPERED PORTIONS, SAID SUPPORTMEDIA BEGIN LODGED IN COMPRESSION IN SAID ANNULAR OPENING, BETWEEN ANDIN CONTACT WITH SAID SLOPING INTERIOR AND EXTERIOR WALL SURFACES, SAIDRELATIVELY SLOPING WALLS AND SAID TAPERED OPENING THEREBETWEEN EXTENDINGALONG A SUBSTANTIAL LONGITUDINAL PORTION OF SAID HOUSING, WHEREBY APORTION OF SAID SUPPORT MEDIA IS SUBJECTED TO INCREASED COMPRESSION WHENSAID HOUSING IS MOVED IN A LONGITUDINAL DIRECTION RELATIVE TO SAIDCASING, THEREBY TENDING TO ARREST LONGITUDINAL MOVEMENT OF SAID HOUSINGRELATIVE TO SAID CASING.
 2. In a catalytic converter for exhaust gasesof the type having a casing with an internal wall surface and gas inletand outlet openings at its respective ends, a fragile housing interiorto said casing in the line of exhaust gas flow having exhaust gaspassages extending longitudinally between and in communication with saidinlet and outlet openings and containing catalyst material, said housinghaving an exterior longitudinal wall surface and being longitudinallymovable with respect to said casing, a resilient support media betweenand engaging the exterior longitudinal wall surface of said housing andthe interior wall surface of said casing to support said housing withinsaid casing and limit relative movement therebetween, the improvementconprising the exterior wall surface of said housing and the opposinginterior wall surface of said casing sloping parallel to each other inone direction along one longitudinal portion of said converter and inthe opposite direction along another longitudinal portion of saidconverter to form therebetween an annular opening with oppositelysloping longitudinal portions, said support media being lodged incompression in said annular opening, between and in contact with saidsloping interior and exterior wall surfaces, whereby a portion of saidsupport media is subjected to increased compression when said housing ismoved in a longitudinal direction relative to said casing, therebytending to arrest longitudinal movement of said housing relative to saidcasing.